Measurements of the rotational temperature of electron‐beam excited nitrogen have been made along the axis of a free jet under various flow conditions. Temperatures calculated from the isentropic flow equations are compared with those derived from the rotational spectra. Discrepancies between the two temperature determinations led to an investigation of the rotational spectrum of nitrogen in thermodynamic equilibrium at 300 and at 78°K. Results of the ``static'' gas measurements are presented which indicate that existing models of the electron‐beam excitation—de‐excitation process may be incorrect.